Nearly 400,000 total knee replacements are performed each year in the United States. This number is expected to grow to nearly 4 million by 2030. All knee replacements require removal of bone on both the tibia and femur. This is necessary in order to remove the damaged cartilage and bone as well as to accommodate the mass of the implant and provide for the proper spacing in the knee joint. The bone which is removed is replaced with a metallic, polymer, or ceramic implant.
Due to limitations in all known materials, the typical life of an implant is approximately 15 years. The lifespan of the implant is highly dependent on patient weight and physical activity. Failure of the implant causes significant pain, immobility, and possible infection. As the implant wears, small particles are released into the surrounding tissue which can cause irritation, possible infection, and loosening of the implant. When the implant fails, the patient must undergo a revision total knee surgery. A revision total knee surgery requires the removal of additional bone in order to properly affix the implant to the bones.
The need to remove bone in order to affix an implant limits the number of knee replacements a patient may receive. Typically after a patient has one revision knee replacement there is no longer a sufficient amount of bone to accommodate another revision surgery. Consequently, patients who need knee replacements must wait until their remaining lifespan is short enough to ensure that they do not outlive a single revision knee replacement. With a combined implant life of approximately 30 years, patients often either put up with the pain or significantly reduce their activity until they believe they have less than 30 years of remaining lifespan. This can have detrimental effects on their health, such as excessive weight gain and increased arthritis of the knee joint.